Friends and colleagues of Iranian American journalist Roxana Saberi, who has been imprisoned, say she is a careful and cautious journalist who covered the complexities of Iran.

PARIS — Poised and articulate, Roxana Saberi took to the airwaves like a natural, delivering a pitch-perfect television report about developments in Iran for the British Broadcasting Corp. in the summer of 2006.

The folks in London were impressed. "She could film, edit, upload video," recalls her boss, Frances Harrison, who was then the BBC's Tehran bureau chief and now lives in London. "She could do radio. She could do television. She could do online."

Those skills made Saberi a rarity: an American journalist based in Iran, covering the country where her father was born and that she loved to explore.

But three years ago, with the Iranian American journalist's star rising, Iranian authorities revoked her press credentials. And when she continued to work and live in Iran, they arrested her in late January, locking her up in Tehran's notorious Evin prison.

The case has perplexed friends and colleagues in Tehran. No charges have been filed, though officials have described her reporting as illegal. On Friday, an Iranian prosecutor said she would be freed within days.

But the detention of the ambitious 31-year-old has stunned and unsettled the journalists who knew Saberi in Tehran. They describe her as a cautious and serious journalist who tried to forge a normal life in the Islamic Republic.

"She is serious as a reporter," said one journalist who knows Saberi but like many interviewed for this report asked not to be named. "Recently, we heard her reporting, which was said to be only straight news, was somehow tolerated by authorities, which is what made the news of her arrest come as a shock."

The daughter of an Iranian-born father and Japanese-born mother, Saberi grew up mostly in Fargo, N.D., where she was a gifted student, musician and athlete. She was also strikingly good-looking, crowned Miss North Dakota in 1998.

Originally hired as a local TV reporter, she quickly grew bored, said her father, a translator and writer still living in Fargo.

"She wanted to do some in-depth journalism," Reza Saberi said in a phone conversation. "She was not satisfied with superficial reports about car accidents and the weather."

During a trip to Washington in 2002, she caught the eye of Simon Marks, president of Feature Story News, an agency that distributes broadcast news packages to radio and television stations around the world. She told him she dreamed of being a foreign correspondent. Throughout her childhood, her father had entertained her with stories about the great Persian poets and ancient kings, and she'd always wanted to explore Iran.

Marks gave her a laptop and camera and hired her as his Tehran bureau chief.

The dual national arrived in Tehran in February 2003. She enrolled in Persian classes and began touring the country, visiting cities and rural hamlets, interviewing liberals and hard-liners, men and women. When an earthquake struck in the southern city of Bam in late 2003, she rushed to the disaster scene, but also returned several times throughout the following year to monitor the town's recovery.

"She very rapidly became a very formidable force," Marks said. "She immersed herself in Iran and traveled the length of the country."

Marks said her reports were gobbled up by his clients, which included Fox News, Radio New Zealand and especially Singapore-based Channel NewsAsia.

Unlike much of Tehran's expatriate community, friends say, Saberi avoided the swirl of parties in private homes and embassies that characterizes the city's underground night life. Instead, she preferred quiet movie nights with friends or strenuous workouts at a gym.

During a birthday party at her home, Saberi entertained guests by playing a stirring rendition of a piano piece she had composed.

"She is soft-spoken, curious in a positive way," said one reporter.

"She is not an extroverted person."

In June 2006, Iranian authorities abruptly revoked her press credentials without explanation. Marks said he tried but failed to persuade Iranian authorities to let Saberi continue to work for his news service.

"I never understood why they shut down a journalist who was so committed to reporting on Iran in all its complexities," he said.

"They never engaged in any dialogue about why they were doing it."

Her father said she had decided to stay in Tehran, refusing to heed his advice to leave the country. She began taking classes in public relations and working on a book, filing occasional reports for National Public Radio and other outlets.

Meanwhile, she tried to persuade officials to let her work.

"Roxana was in negotiation with authorities for a long time after her press card was taken back, hoping she could change their mind," said one friend. "She would say she was never told if she had made any specific mistake in her stories."